Currently, there are no molecular screening tools available that can identify the patients at high risk for breast cancer development or local recurrence. Of interest, however, is that numerous studies have suggested the existence of genetic alterations (LOH, chromosomal abnormalities, specific gene mutations) in histological non-malignant breast tissue, identical to those found in adjacent tumor, in up to 60% of patients. These data suggest that there are numerous genetic alterations that accumulate prior to the histological development of cancer, although the frequency, identity, and location of these alterations within the normal appearing breast are still poorly understood. We hypothesize that genetic alterations exist in non-malignant breast tissue and that they will produce phenotypic alterations in gene expression that may be useful in predicting breast cancer risk. cDNA microarrays will be used to identify a set of genes whose expression profile predicts cancer risk in histologically non-malignant breast tissue. As a first step towards the detection of molecular screening markers for sporadic breast cancer, we plan to investigate the non-malignant breast tissue adjacent to cancer in patients known to be at increased risk for cancer recurrence both in the ipsilateral and contralateral breasts. This will be accomplished by a comprehensive analysis of genetic, epigenetic and gene expression alterations performed simultaneously on breast tumors and normal associated breast tissue. Whereas the principal goal is identifying a gene expression pattern for normal tissues at high risk for developing cancer, we will also develop rich databases to decipher patterns characterizing breast tumors and their clinicopathologic features (including survival and recurrence data) as well as benign breast pathology. We then plan to evaluate the behavior of these high-risk genes in patients undergoing adjuvant therapy to reduce cancer risk. Specific Aim I. To identify the frequency and geographic distribution of abnormal genetic (DNA), epigenetic (DNA methylation) and molecular (RNA) signatures, within zones of histologically non-malignant breast tissue adjacent to invasive cancer derived from mastectomy specimens (n = 100). Specific Aim II. Determine if genetic and epigenetic alterations as well as gene expression alterations identified in Aim I can be detected in the contralateral normal breast in patients undergoing bilateral mastectomy for ipsilateral cancer(n = 50). Specific Aim III. To identify genetic, epigenetic and gene expression alterations in normal and tumor tissues from patients undergoing mastectomy for intraductal neoplasia (n = 50). Specific Aim IV. Determine if the expression of high-risk gene sets (identified in Aims I, II, and III) in the contralateral, untreated breast are affected by adjuvant chemotherapy and/or hormonal therapy in serial biopsy specimens (n = 50) taken pre- and post- therapy. [unreadable] [unreadable]